Method for the introduction of inorganic solid bodies into hot liquid melts

ABSTRACT

A method is disclosed for the introduction of inorganic solid bodies into hot, liquid melts, whereby inorganic solid bodies are added to a plastic containing a hydrocarbon and the mixture obtained is added to the hot, liquid melt.

The invention relates to a process for the introduction of inorganicsolids into hot liquid melts.

Hot liquid melts are understood here as meaning metallurgical meltsand/or slags found e.g. in a furnace.

In metallurgy, fluxes often have to be added to the hot liquid metals orslags in the various processing stages. This applies to both the ironand steel industry and non-ferrous metallurgy. Fluxes are used e.g. inthe following metallurgical processes:

-   -   Primary metallurgy: products for liquefying the slag-forming        additives during the smelting phase, and fluxes for the blast        furnace industry for the purpose of prolonging the durability of        the refractory lining of the blast furnace hearth.    -   Secondary metallurgy: fluxes for the top slags of melts for the        purpose of adjusting the metallurgical properties of the melts        to the desired values. It is possible here to use fluxes which        have a direct chemical influence on the properties of both the        liquid metals and the liquid slags, as well as fluxes which have        a physical influence on the consistency of the particular        reactants. Normally, in the case of a physical influence, a        depression of the melting point of the slags is sought in order        to influence the metallurgical reaction kinetics of the systems        with the aim of enabling the reaction in the first place and        furthermore accelerating it.    -   Tertiary metallurgy: In this final phase of the metallurgical        production stages, at the last possible point immediately        upstream of the pouring process, an attempt is made both        chemically to adjust the properties of the end products, by        adding metallurgically effective substances, and physically to        influence the solidification structure of the particular metals        to be poured, by adding exogenous nuclei.

To be able to introduce the fluxes into the hot liquid melts (metals orslags) in the respective processing stages, the following knowntechnologies, inter alia, are used:

-   -   Addition of the normal, coarse fluxes from a variety of usually        fully automatic weighing and bunker systems via simple gravity        conveyors and hopper systems.    -   Addition of the fluxes in sack-like forms of packaging, e.g.        sacks or big bags, either by hand or by means of cranes.    -   Addition of the fluxes by means of filler wires, the cavities of        the filler wires (often consisting of a metallic alloying agent)        containing the particular flux(es).

Addition of the fluxes by means of injection equipment, which generallyconsists of a weighing and bunker system with a downstream gasoverpressure injection system. Gas overpressure systems are mechanicallyadapted to the particular requirements of the intended applications(e.g. high-pressure or low-pressure plant). The carrier gases used canbe compressed air, nitrogen or other gases, as required. If fluxes areto be injected into the furnace (e.g. blast furnace) without directliquid contact, the solid flux can be introduced into the furnacechamber against the furnace pressure via a fixed injection lance. Ifsolid fluxes are to be injected into the furnace (e.g. electric furnace)in the boundary layer between liquid iron and liquid slag, for thepurpose of foaming the slag, the injection pressure has to be adapted tothe physical proportions of the metallurgical system. Also, theinjection lance must remain movable in this case in order to be able toadapt flexibly to the respective phases of the scrap smelting process.

A common feature of all the systems is that the physical consistency ofthe fluxes exerts a decisive influence on the technology of addition.Because of their intrinsic weight, coarse products fall withoutdifficulty through the rising process gases into the smelting area. Onthe other hand, products of medium particle size are sucked up by thebuoyancy forces of the process gases or the suction forces of the filterplants before they can develop their desired action in the liquid media.For this reason they are first packed in sacks or big bags and thenintroduced into the system all at once. Even if they are first packed inbig bags or sacks, fine fluxes still cannot be protected from beingdrawn away from the liquid media by the ascending convection current orsuction forces after the sacks have burnt off, and from accumulating inundesirable manner in the filter plants.

The object of the invention is to overcome the disadvantages of thestate of the art and provide a novel process by which fine inorganicfluxes, in particular, can be introduced into metallurgical smeltingsystems.

The object is achieved by a process for the introduction of inorganicsolids (=fluxes) into hot liquid melts wherein inorganic solids areadded to a hydrocarbon-containing plastic and the resulting mixture isintroduced into the hot liquid melts.

The inorganic solids are preferably added in the form of fine particles.90% of the inorganic solid particles have sizes particularly preferablyof 0.01 μm to 5 mm and very particularly preferably of 0.1 μm to 2 mm.

The proportion of inorganic solids in the plastic is preferably 0.5 to90 wt. %, particularly preferably 2 to 70 wt. % and very particularlypreferably 5 to 50 wt. %, based in each case on the mixture.

The inorganic solids (=fluxes) used are preferably titanium-containingsubstances and/or substances containing iron oxide, aluminium oxide,magnesium oxide, calcium oxide, silicates or slag-forming additives,individually or as a mixture. In particular, the substances containingiron oxide, aluminium oxide, magnesium oxide, calcium oxide, silicatesor slag-forming additives can be industrial residues. Very particularlypreferably, the flux contains synthetic titanium dioxide.

Apart from hydrocarbons, the plastic preferably also contains theelement nitrogen. For economic reasons the plastic used is preferablyold plastic.

The mixture of plastic and flux can be prepared in a variety of ways:

-   -   The plastic is mixed in solid form (preferably as granules,        matrix agglomerate or pot agglomerate) with the inorganic        solids. The inorganic solids are preferably added to the plastic        during the production of the plastic granules. The flux adheres        to the plastic surface in the mixture obtained. This mixture is        introduced into the hot liquid substances (metallurgical melts        and slags).    -   The plastic is mixed in liquid (molten) form with the inorganic        solids. The mixture of molten plastic and inorganic solids        (=fluxes) is preferably cooled so that it solidifies. The        plastic/flux mixture can then be ground or shredded.

When the plastic/flux mixture is in the appropriate form (e.g. as powderor granules), the mixture can preferably be introduced into the hotliquid melts by injection. The plastic/flux mixture can also be used inthe form of lumps. For this purpose shaped bodies of the particulardesired dimensions can be produced from the mixture by pressing.

One advantage of the process according to the invention is that, bybeing introduced in a mixture with the plastic, the flux can beproportioned very well and introduced into the hot liquid melts individed form. This applies especially to fluxes in the form of dust.Industrial residues in the form of dust, containing iron oxide,aluminium oxide, magnesium oxide, calcium oxide, silicates orslag-forming additives, can thus be utilized industrially. Theseresidues are preferably mixed with synthetic titanium dioxide and then,as described, with the plastic.

Another advantage of the process according to the invention is that theplastic not only serves as a vehicle for the flux, but can also act as areducing agent and/or energy carrier (partially replacing heavy oil orcoal). In the case where the flux contains titanium, especiallysynthetic titanium compounds, the plastic contributes in the hot liquidmelt to the desired formation of titanium carbides and, if the elementnitrogen is present, titanium nitrides and titanium carbonitrides. Thesecompounds improve the refractory properties of the furnace wall in e.g.furnace systems.

1-15. (canceled)
 16. A process comprising adding inorganic solids to ahydrocarbon-containing plastic and introducing the resulting mixtureinto a liquid melt.
 17. A process according to claim 16, wherein 90% ofthe inorganic solid particles have sizes of 0.01 μm to 5 mm.
 18. Aprocess according to claim 17, wherein 90% of the inorganic solidparticles have sizes of 0.1 μm to 2 mm.
 19. A process according to claim16, wherein the proportion of inorganic solids in the plastic is 0.5 to90 wt. %.
 20. A process according to claim 19, wherein the proportion ofinorganic solids in the plastic is 2 to 70 wt. %.
 21. A processaccording to claim 16, wherein the inorganic solids are at least onesolid selected from the group consisting of a titanium-containingsubstance, iron oxide, aluminum oxide, magnesium oxide, calcium oxide, asilicate, and a slag-forming additive.
 22. A process according to claim21, wherein the flux contains synthetic titanium dioxide.
 23. A processaccording to claim 16, wherein the plastic comprises nitrogen.
 24. Aprocess according to claim 16, wherein the plastic used is old plastic.25. A process according to claim 16, wherein the plastic is mixed insolid form with the inorganic solids.
 26. A process according to claim16, wherein the plastic is mixed in molten form with the inorganicsolids.
 27. A process according to claim 26, further comprising coolingthe mixture until the mixture solidifies to form a solidifiedplastic/flux mixture.
 28. A process according to claim 27, wherein thesolidified plastic/flux mixture is ground or shredded.
 29. A processaccording to claim 16, wherein the plastic/flux mixture is introducedinto the hot liquid melts by injection.
 30. A process according to claim16, wherein the plastic/flux mixture is introduced into the hot liquidmelts in the form of lumps.